U.S. Pat. No. 4,4,218,543 describes the production of reaction injection molded (RIM) products using reaction mixtures of diisocyanates or polyisocyanates based on 4,4'-isocyanatodiphenyl methane, aromatic polyamines, and relatively high molecular weight polyhydroxyl compounds.
Recent advances in the RIM area have been directed to the substitution of so-called "amino-polyethers" for all or a portion of the relatively high molecular weight polyhydroxyl compounds. See, e.g., U.S. Pat. Nos. 4,396,729, 4,433,067, 4,444,910, 4,530,941, 4,590,219 and 4,774,263; and German Offenlegungsschriften 3,215,907 and 3,215,909. Typically, the isocyanates used with the amino-polyethers have included (i) liquid products made by reacting 4,4'-diphenylmethane diisocyanate with tripropylene glycol, (ii) liquid modified 4,4'-diphenylmethane diisocyanates containing carbodiimide groups and (iii) prepolymers from 4,4'-diphenylmethane diisocyanate and polyethers (see the first five references noted in this paragraph). U.S. Pat. No. 4,590,219 also described the use of a prepolymer from 4,4'diphenylmethane diisocyanate and a diethylene glycol adipate (having an OH number of 42).
U.S. Pat. No. 4,857,561 describes prepolymers based on neopentyladipate and the use of such prepolymers in a RIM process.
Recently, our company has evaluated the use of a prepolymer derived from 4,4'-diphenylmethane diisocyanate, a polyester (having a molecular weight of 2000 and produced from adipic acid, ethylene glycol, and butanediol), and a carbodiimidized 4,4'-diphenylmethane diisocyanate. Although this particular prepolymer, when sued in a RIM process with amino polyethers yields products having excellent physical properties, it still suffers from some drawbacks. Specifically, the prepolymer is generally incompatible with the amino polyethers. This results in poor mixing and the production of non-homogeneous parts. Additionally, when zinc stearate internal mold release agents are used, the hydrolytic stability of the molded part is adversely affected.
U.S. Pat. Nos. 4,284,750 and 4,525,424 describe the use of a polyester based on cyclohexane dimethanol in the production of flexible magnetic recording media.